Wide-temperature range greases



2,977,301 WIDE-TEMPERATURE RANGE GREASES Charles R. Bergen, Schenectady, N.Y., and William P. Scott, Richard M. Tillman, and Warren W. Woods, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware .No Drawing. Filed Aug. 21, 1958, Ser. No. 756,302

22 Claims. (Cl. 252-18) The present invention relates to improved wide-temperature range greases and, more particularly, relates to such greases containing an agent for reducing extreme thixotropy therein.

Greases prepared by the use of the normal soap-forming ingredients, such as the acids derived from animal fats or vegetable oils, exhibit phase changes with increasing temperature up to a point at which the soap dissolves or at least forms a colloidal dispersion in the lubricating oil base with consequent loss of mechanical structure responsible for grease-like properties. Furthermore, these greases generally do not reform spontaneously upon cooling. As a result, such greases are unsuitable for use in the lubrication of bearings operated at elevated temperatures, such as those used in certain aircraft mechanisms and the like.

Several methods of preparing wide-temperature range greases have been proposed in the prior art. One proposal incorporates certain salts of aromatic acids in the grease composition such as sodium benzoate, which apparently forms complexes with the normal soap-forming acids. While these additives impart heat stability to the resulting grease, it is necessary to heat such grease compositions during the process of manufacture to a temperature of at least 500 to 600 F. This is a disadvantage because temperatures in this range involve fire hazards and promote oxidative degradation of the oil carrier. Another method heretofore proposed for the preparation of heat-stable greases involves the formation of an inorganic hydrogel and subsequently replacing the interstitial water contained in the gel with an oleaginous liquid vehicle. Two procedures have been suggested for the replacement of the interstitial water. In one, anaerogel is first formed by displacing the water with a solvent which is soluble in both water and oil. In the second procedure the hydrogel is heated in the presence of a surface-active agent dissolved in an oleaginous liquid vehicle; U.S. latent 2,625,508 to Fred H. Stross describes this procedure. Whichever procedure is used, several disadvantages are inherent in the process, as, for example, a hydrogel is bulky and difiicult to handle, the gel must be washed to remove salts, and hydrogels contain a large amount of water which must be removed.

In order to prepare greases which are satisfactory over the temperature range of -100 F. to above-450 B, it is. necessary to use as base fluids those materials which inthemselves have a satisfactory viscosity-temperature relationship over the temperatures involved. At the presout time this requirement limits the base'fluids to the synthetic types. 7

Normal thixotropy is anessential characteristic of greases; however, in the extreme, thixotropy causes an undesirable hardening during storage; and under working conditions (such as existin a bearing), an intolerable softening occurs, allowing the grease to escape from the. rubbing surfaces. It'is desirable to have a grease which has relatively the same penetration under extreme workice extreme thixotropy and work stability are not'the same, for all practical purposes in this disclosure they are considered equivalent. I

It is an object of the present invention to provide improved grease compositions operable over a wide temperature range. It is still another object of the present invention to provide such improved grease compositions which do not exhibit extreme thixotropy. Other objects will become apparent as the invention is hereinafter more thoroughly described.

Broadly stated, the improved grease compositions of the present invention comprise a major amount of an oleaginous vehicle, a minor amount of a grease-forming agent, said grease-forming agent consisting of a colloidal dispersion of both calcium carbonate and the reaction product of calcium carbonate and alow molecular weight polycarboxylic acid in 'the presence of a metal sulfonate, and a minor amount "of an agent for reducing extreme thixotropy in said' grease compositions.

Materials which are suitable for use as an oleaginous vehicle, or base fluid, include the following:

While at the present time synthetic fluids are thepre ferred oleaginous vehicle, this invention is not limited thereto. Other materials which have the necessary viscosity-temperature relationship over the temperature range desired could fall within the spirit and scope of this invention. e i

The grease-forming agent of the present invention is prepared by forminga colloidal dispersion of calcium carbonate in calcium sulfonate and reacting therewith an appropriate amount or a low-molecular'weight polycarboxylic acid. If desired, the reaction may take place in the presence of an amount of the base fluid, wherein the grease-forming agent is formed in situ.

The colloidal dispersion of calcium carbonate in cal cium sulfonate'is prepared as follows:

(a) a methanolic solution of calcium sulfhydrate is .pre-Tf pared,

(b) a solution is then prepared containing the methanolic calcium sulfhydrate and a sulfonic acid solution in benzene as a solvent, f (c) the solution is blown with carbon dioxide,

(d) the desired base fluid is added and the volatile solvents removed.

The preparation of this colloidal dispersion of calcium},

carbonate in calcium sulfonate is disclosed also by Robert L. Carlyle in S.N. 629,229, filed December 19, 1956fnow US. Patent No. 2,937,991

The calcium sulfhydrate is prepared by adding calcium oxide, calcium hydroxide, or the hydrates of calciunjhy droxide, to an alcohol and blowing" withhydrogen sulfide;

Suitable alcohols include those of thealiphatic primary series having from 1 to ,6 carbon atoms. Of these" alcoe hols, methanol is' preferred. The solution is to remove impurities.

Patented Mar. 28, 1961 n m s e Any of the sulfonic acids, or sulfonates, normally used in the manufacture of lubricating oil additives may be used as the dispersing agent in the grease-forming agent. Examples of these materials would include the mahogany sulfonates, diwaxbenzene sulfonates, dinonylnaphthalene sulfonates and postdodecylbenzene sulfonic acid. Postdodecylbenzene is a by-product of the manufacture of dodecylbenzene, being the bottoms after distilling the dodecylbenzene and postdodecylbenzene overhead. This material is also known as stripped postdodecylbenzene, the terms being synonymous in this disclosure. For the sake of simplicity, postdodecylbenzene is often referred to as PDB, and will be so used in this disclosure.

Postdodecylbenzene consists of monoalkylbenzenes and dialkylbenzenes in the approximate mole ratio of 2 to 3. Its typical physical properties are as follows:

Specific gravity at 38 C 0.8649

Suitable low-molecular weight polycarboxylic acids for use in this invention include the following:

3-methyl glutaric acid Itaconic acid Pyromellitic acid 2-methyl adipic acid 3-tertiary butyl adipic acid 3-tertiary amyl adipic acid Octyl adipic acid Furoic acid Mercapto succinic acid 2,2-dibromo succinic acid 5-methyl-4-cyclohexane-1,Z-dicarboxylic acid (m-Phenylenedioxy) diacetic acid Benzylmalonic acid Terephthalic acid Thiodiglycolic acid Of these, 3-methyl glutaric acid is preferred.

Two types of materials have been found to be suitable for use as agents for reducing extreme thixotropy. These are the methacrylate ester co-polymers' and the silicone polymers. The methacrylate ester co-polymers used in this invention have the formula where R is a mixture of alkyl groups containing from 4 to 20 carbon atoms and n is a number providing a molecular weight of the co-polymer of about 15,000 to 40,000. Commercial methacrylate ester co-polymers which may be used are those sold under the Acryloid" trade name. Specific examples of these materials include the following: Acryloid 618, Acryloid 710, Acryloid 763, and Acryloid 794.

Suitable silicone polymers which maybe used include the polymethylsiloxanes, phenyl substituted polymethylsiloxanes, and chlorinated polysiloxanes. Suitable commercially available materials are those sold under'the.

DC trade name by Dow-Corning, as for example DC 510 (phenyl substituted polymethylsiloxane), DC 200 (polymethyl siloxane), and DC 371 (polymethylethyl siloxane). Other suitable commercially available materials are those sold by General Electric, for example SF-81" and SF-96, and by Union Carbide and Carbon, for example, L-45" and L-522. These materials are available in various viscosity or molecular weight grades, such as 50 centistokes, etc.

In order to disclose more clearly the nature of the present invention and the advantages thereof, reference will hereinafter be made to certain specific embodiments which illustrate the flexibility of the herein described process. It should be clearly understood, however, that this is done solely by Way of example and is not to be construed as a limitation upon the spirit and scope of the appended claims.

EXAMPLE I Preparation of colloidal dispersion of calcium carbonate in calcium sulfonate A methanolic solution of calcium sulfhydrate was prepared as previously described.

Materials used:

PDB sulfonic acid in naphtha (0.787 milliequivalents per gram-total acidity; 28.7

percent active) grams 2926.8 Benzene (solvent) ml.. 3000 Calcium sulfhydrate in methanol (4.2 milliequivalents Ca per gram) grams 1641 Di-Z-ethyl hexyl azelate (base fluid) do 1607.8

Weight percent CaCO 8.4 Ca PDB sulfonate 32.5 Di-Z-ethyl hexyl azelate 59.1

The material had an actual base number (acetic) of 102, as compared to a theoretical one of 94.4.

EXAMPLE II Preparation of base grease Materials used:

Procedure: The Group A materials were added to a suitable reaction vessel. A solution was prepared of Group B materials, and this was added to the reaction vessel while stirring the contents. The solvents were removed by heating to C. while stirring and blowing with nitrogen.

This grease had a theoretical composition as follows:

Weight percent Ca PDB sulfonate 11.54 CaIcium-B-methyl glutarate 7.3 Calcium carbonate 0.7

Di-Z -ethyl hexyl azelate 80.46

awnm EXAMPLE-111:}

The product t Example. 11 wasfound' to? Iexhibitjex hibit extreme thixotropy. Methacrylate ester oo-polymers in various amounts andvof various compositions were added to this base grease. This was donesimply by adding a known percentage of methacrylate. ester. co-'. polymers to the base grease' and homogenizing theresulting-product. The results of the useof the meth Calcium carbonatedispersion (1'09.5 g..CaCO 423.7 g. Ca PDB sulfonate, 'balancedi-2- ethyl hexyl azelate) -..grams 13.04 Di-Z-ethyl hexyl azelate do 1281 Benzene 13 1 Acetone solution of 3-methyl glutaric acid (1 ml.'=0.2' g. acid) -ml 683 Acetone ml 47g, Benzene ml 1361 Procedure: The same procedure as gused in. Example II was employed here.

This grease had atheoretical composition as; follows:

Weight percent Ca PDBsulfonate 15.91

Ca-Z-methyl glutarate 6.46

CaCO g I 0.6

Di-Z-ethyl hexyl azelate 77:03

EXAMPLE V' The ,productyofllixample wasgfonnd' tohave extreme thixotropy. Varying amounts of a pheny ubistituted polymethyl-siloxaue (DC-51 -50 c.s. grade) were added to the base grease. Again, this was done simply by adding a known percentage and homogenizing the resulting product. Penetration data for this example is shown in Table II.

TABLE II Use of silicone polymer for reducing extreme thiwotropy Percent Penetration Strokes 1 Addition Base Grease oi Silicone Fluid 60 3.000 10,000 100,000

Example IV 0 205 355 Fluid Do. 1 300 370 Fluid Do. 3 290 320 325 340 Do- 0 280 305 305 310 Do. 9 280 290 300 305 Do 12 275 290 305 305 l A.S.T.M. Method D217.

, sisting of aliphatic diestcrs, polyesters, and silicate esters, a minor amount of a grease-forming agent, said grease 15 forming agent consisting of a colloidal dispersion in an Preparation of grease. containing, silicone polymen Materials; used:

A "Qalciurn carbonate dispersion (8.5% CaCO a 26. 65% Ca- PDB sulfonate) grams- 1086.4 DiZethylv hexyl azelate do .....1116.3 11 B z e i 1134 Acetone solution of 3-methylglutaric acid (113.9 g. acid) ml.... 5 70v 'Acetone ml I 565 Benzene ml 1134' C DC--5l0.- (50 cls.) .grams 197.2

Procedure:' The. Group A' materials were added to a suitable reaction. vessel. A solution was prepared of Group B materials, and thistwas addedrto the reaction vessel while stirring the contents. Thesolvents were removed by heating to "v C. At this stage the DC-SlO was added- (This is 8, percent by-weight of-theoretical:

product.) The. product was stirred and heated to I C. while blowing dry air over the grease.

This grease had a theoretical composition as follows:

Weight percent Ca PDB sulfonate v 11.74 C'a-3-methyl glutarate 5.82 CaCO 0.56 Di-2ethyl hexyl azelate 73.88 DC-S 10- 8.0

The penetration data on this grease is-shown in Table III. An additional amount of silicone. polymer wasadded to a portion ofthe product. by adding a known amount. and homogenizing the re-. sulting product. Penetrationdata for this example is shown in Table III. I

TABLE In Use of silicone polymer as work stability improver Percent "Penetration Strokes 1 Base Grease Addition of Silicone Fluid 60 3,000

Example V. 8 340 300 Do 15 325 325,

: A.s.T.M. Method D217. 7

The data presented in Table I indicate clearly that the I use: of methacrylateester co-polymers' reduces" extreme 3 thixotrcipy and improves the work-stability of t hese'par j j ticular greases. The data-inLTable II indicate that sills cone polymers also function very-well tor this; purpose. Example VI and the resulting data in Table III have been included to demonstrate'that silicone polymers function as a work stability agent'for this grease. The grease of Example VI differs from the grease of Ex-l ample IV primarily in the amount of sulfonate present.

While particular embodiments of the invention have been described. it will be understood, of course, that the invention is not limited thereto, since many modifications may be made; and it is, therefore, contemplated to cover by the appended claims any such modifications V p as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent isz; I 1. A grease composition comprising a major amount of a synthetic lubricant selected from the'group con This. was'done simply.

oil-soluble metal sulfonate of both calcium carbonate and the reaction product of calcium carbonate and a low molecular-weight polycarboxylic acid selected from the group consisting of 3-methyl glutaric acid, itaconic acid, pyromellitic acid, 2-methyl adipic acid, 3-tertiary butyl adipic acid, 3-tertiary amyl adipic acid, octyl adipic acid, furoic acid, mercapto succinic acid, 2,2-dibromo succinic acid, 5-methyl-4-cyclohexane-1,Z-dicarboxylic acid, (m-phenylenedioxy) diacetic acid, 'benzylmalonic acid, terephthalic acid, and thiodiglycolic acid in the presence of an oil-soluble metal sulfonate, wherein the amount of said acid is equivalent to that which varies from 37 to 85 percent of that theoretically required for neutralization of said calcium carbonate originally present, and a minor amount of an agent for reducing extreme thixotropy in 'said grease composition, said agent being selected from the group consisting of methacrylate ester co-polymers having molecular weights in the range of 15,000 to 40,000 and silicone polymers.

2. A grease composition as defined in claim 1, wherein the synthetic lubricant is an aliphatic diester. 3. A grease composition as defined in claim 1 wherei the synthetic lubricant is an aliphatic polyester.

4. A grease composition as defined in claim 1 wherein the synthetic lubricant is an aliphatic silicate ester.

5. A grease composition as defined in claim 1 wherein the low molecular weight polycarboxylic acid is 3-methyl glutaric acid.

6. A grease composition comprising a major amount of an aliphatic diester, a minor amount of a grease-forming agent, said grease-forming agent consisting of a colloidal dispersion in an oil-soluble metal sulfonate of both calcium carbonate and the reaction product of calcium carbonate and 3-methyl glutaric acid in the presence of an oil-soluble metal sulfonate, wherein the amount of said acid is equivalent to that which varies from 37 to 85 percent of that theoretically required for neutralization of said calcium carbonate originally present, and a minor amount of an agent for reducing extreme thixotropy in said grease composition, said agent being selected from the group consisting of methacrylate ester co-polymers having molecular weights in the range of 15,000 to 40,000 and silicone polymers.

7. A grease composition as defined in claim 2, wherein the agent for reducing extreme thixotropy in said grease composition is a methacrylate ester co-polymer having a molecular weight in the range of 15,000 to 40,000.

8. A grease composition as defined in claim 2, wherein the agent for reducing extreme thixotropy in said grease composition is a polymethylsiloxane.

9. A grease composition as defined in claim 2, wherein the agent for reducing extreme thixotropy in said grease composition is a phenyl substituted polymethylsiloxane.

10. A grease composition as defined in claim 2, wherein the agent for reducing extreme thixotropy in said grease composition is a chlorinated polysiloxane.

11. A grease composition as defined in claim 3, where in the agent for reducing extreme thixotropy in said grease composition is a methacrylate ester co-polymer having a molecular weight in the range of 15,000 to 40,000.

12..A grease composition as defined in claim 3, wherein the agent for reducing extreme thixotropy in said grease composition is a polymethylsiloxane.

13. A grease composition as defined in claim 3, wherein the agent for reducing extreme thixotropy in said grease composition is a phenyl substituted polymethylsiloxane.

14. A grease composition as definedin claim 3, wherein the agent for reducing extreme thixotropy in said grease compostion is a chlorinated polysiloxane.

' 15. A grease composition as defined in claim 4, where in the agent for reducing extreme thixotropy in said grease composition is a methacrylate ester co-polymer having a molecular weight in the range of 15,000 to 40,000.

16. A grease composition as defined in claim 4, wherein the agent for reducing extreme thixotropy in said grease composition is a polymethylsiloxane.

M 17. A grease composition as defined in claim 4, where in the agent for reducing extreme thixotropy in said grease composition is a phenyl substituted polymethylsiloxane.

18. A grease composition as defined in claim 4, wherein the agent for reducing extreme thixotropy in said grease composition is a chlorinated polysiloxane.

19. A grease composition as defined in claim 4, wherein the agent for reducing extreme thixotropy in said grease compositionis'a methacrylate ester co-polymer having a molecular weight in the range of 15,000 to 40,000. a

20. A grease composition as defined in claim 6, where in the agent .for reducing extreme thixotropy in said grease composition is a polymethylsiloxane.

21. A grease composition as defined in claim 6, wherein the agent for reducing extreme thixotropy in said greasecomposition is a phenyl substituted polymethylsiloxane.

22. A grease composition as defined in claim 6, wherein the agent for reducing extreme thixotropy in said grease composition is a chlorinated polysiloxane.

Greases, Boner-Reinhold Pub. Corp., N.Y., 1954, pp. 443 and 445. 

1. A GREASE COMPOSITION COMPRISING A MAJOR AMOUNT OF A SYNTHETIC LUBRICANT SELECTED FROM THE GROUP CONA MINOR AMOUNT OF A GREASE-FORMING AGENT, SAID GREASEFORMING AGENT CONSISTING OF A COLLOIDAL DISPERSION IN AN OIL-SOLUBLE METAL SULFONATE OF BOTH CALCIUM CARBONATE AND THE REACTION PRODUCT OF CALCIUM CARBONATE AND A LOW MOLECULAR WEIGHT POLYCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF 3-METHYL GLUTARIC ACID, ITACONIC ACID, PYROMELLITIC ACID, 2-METHYL ADIPIC ACID, 3-TERTIARY BUTYL ADIPIC ACID, 3-TERTIARY AMYL ADIPIC ACID, OCTYL ADIPIC ACID, FUROIC ACID, MERCAPTO SUCCINIC ACID, 2,2-DIBROMO SUCCINIC ACID, 5-METHYL-4-CYCLOHEXANE-1,2-DICARBOXYLIC ACID, (M-PHENYLENEDIOXY) DIACETIC ACID, BENZYLMALONIC ACID, TEREPHTHALIC ACID, AND THIODIGLYCOLIC ACID IN THE PRESENCE OF AN OIL-SOLUBLE METAL SULFONATE, WHEREIN THE AMOUNT OF SAID ACID IS EQUIVALENT TO THAT WHICH VARIES FROM 37 TO 85 PERCENT OF THAT THEORETICALLY REQUIRED FOR NEUTRALIZATION OF SAID CALCIUM CARBONATE ORIGINALLY PRESENT, AND A MINOR AMOUNT OF AN AGENT FOR REDUCING EXTREME THIXOTROPY IN SAID GREASE COMPOSITION, SAID AGENT BEING SELECTED FROM THE GROUP CONSISTING OF METHACRYLATE ESTER CO-POLYMERS HAVING MOLECULAR WEIGHTS IN THE RANGE OF 15,000 TO 40,000 AND SILICONE POLYMERS. 